In the past, many electroplating baths have been disclosed for providing bright zinc deposits on metallic substrates for use in many industrial applications. Initially, one of the most widely accepted commercial baths utilized a cyanide electrolyte. These cyanide-based baths, while highly effective for electroplating zinc, present significant objectionable features, not the least of which are toxicity and difficulty of waste disposal unless expensive waste treatment equipment is employed.
To overcome many of the objectionable features of cyanide-based baths, sulfate or chloride electrolytes have been proposed; see, e.g., U.S. Pat. Nos. 3,729,394; 3,594,291; 3,694,330 and 3,855,085. In all of these baths, however, ammonium ions and/or chelates are taught to be desirable and/or necessary to provide bright zinc deposits. The presence of ammonium ions and/or chelating complexforming compounds significantly increases the difficulty of eliminating heavy metals from spent baths because of the ability of such compounds to complex with heavy metal ions.